Method and device for impregnating especially natural stones

ABSTRACT

Method and device for impregnating plates (5) with a dispersion (D), whereby the plates (5) are saturated with dispersant (M) in a device (1) and the plates (5) are dried with dry air in a drying system (2) from the surfaces (51) to be impregnated down to a predetermined depth and then the dispersion (D) is introduced with an application device (3) into the dried area and the plates (5) subsequently dried. 
     The application roller (3) is located in a vacuum chamber (7). The plates (5) are conveyed among the various devices (1, 2, 3, 4) with a continuous conveyor (6), a conveyor belt for example.

Impregnating absorbent materials, especially natural stones withdispersed materials, especially cross-linked plastics, is known. Thedispersion is applied to the surface, dried and extensively freed ofdust and detritus, of the stone, subsequent to which the dispersionpenetrates into the capillaries, so that the dispersed material becomesembedded in the capillaries and hardens there as soon as the dispersantbecomes distributed or evaporates.

The known method is employed for both the tops and bottoms of pavingstones intended for application as wall or floor coverings, with thelatter in particular needing to be protected from the uptake of moisturefrom the ground and mortar. It has in fact been demonstrated thatmoisture from the ground and/or mortar releases constituents that aretransported through the paving stones as far as their surface, wherethey are enriched by the constant evaporation of the solvent water anddiscolor the stone themselves or as the result of chemicaltransformation of the minerals in the stone. This process is a specialdrawback in that it continues uninterrupted for years. Natural stonesare as a countermeasure impregnated from the "bottom," where, that is,they come into contact with the mortar or adhesive, with a waterproofemulsion. Dispersions based on acrylic resin and with a mean particle ordroplet size smaller than the mean width of the pores in the stone areemployed for example for this purpose.

The drawback of the known method is that relatively large amounts ofdipersion must be applied to obtain an impregnation or insulation thatleads to satisfactory sealing. Otherwise, the impregnation will not forma reliable seal.

The object of the invention is to disclose a method that allows animpregnation leading to reliable sealing at relatively low consumptionof the dispersion in a simple way.

This object is attained in that the capillaries are saturated withdispersant (water), the surface to be sealed then dried subject tocontrol down to a slight depth, and then the surface saturated with thedispersion.

The method causes only a slight amount of dispersion to be accepted bythe dried area, which remains saturated until the dispersed materialsets. No indefinitely small concentration can occur in such a shallowarea because the deeper area is already saturated with dispersant.

The method can also be integrated to great advantage into the cutting,grinding, and drying of paving stones. Since cutting and grinding ortrimming is accompanied by the addition of water, the stone will alreadybe subsequently saturated with water. Thus, regulated drying, dustremoval, and saturation with dispersion will follow that stage of themethod.

It is practical for the dispersion to be applied with sponge rollers orbrushes to ensure that, given adequate dwell time, the amount ofdispersion necessary for saturation will always be absorbed, ensuring asatisfactory seal. The amount will automatically adjust to need inaccordance with the particular level of dryness and porosity of thesurface.

Another advantage of sealing directly subsequent to cutting is theelimination of one manual operation and subsequent drying prior tolaying the stones. If this drying, which must be carried out prior tolaying, is not completed, which can easily occur, either the mortar oradhesive will not adhere properly subject to certain conditions or thedispersion will migrate into the mortar and deteriorate the seal.

The method and one device for carrying it out in the case of coating oneside will now be described by way of example with reference to thefigures. The method can be varied for coating all surfaces of the stoneand for coating stones that are already in place.

FIGS. 1 and 3 illustrate a continuous impregnation layout and

FIG. 2 a concentration graph.

The device illustrated in FIG. 1 is directly downstream of a knowncutting device 1, in which the paving stones are saturated with waterwhile being cut. If no cutting occurs, an immersion or spray device thatthe stone 5 can be left in long enough to be saturated with dispersant Mwill be adequate.

The saturated stone is advanced through a drying system 2 by a conveyor6 to dry off "bottom" 51, which is the surface to be impregnated andwhich will latter be in contact with the mortar, as well as, preferably,the sides, to a predetermined depth. The temperature, air speed, anddrying or through-pass time must be adjusted to the type of stone and tothe desired drying depth in a known way. Forced drying by means ofhigh-speed air with its temperature raised through a heat register H andat a briefer through-put is preferred in order to almost entirelyprevent the dispersant from returning from inside and to establishsatisfactory demarcation of areas 52 and 53. The surface 55 of the stonethat is not to be dried rests on a covering base, conveyor 6 forinstance.

Subsequent to drying, the surfaces that are to be impregnated arecleaned in a dust-removal device 21 by brushes and vacuum devices tocompletely clear the pores.

The dried surfaces are then saturated with dispersion D, which is keptin a reservoir 33, in which it is maintained by controls at a definitelevel and whence it is transferred in a way that is known from printingtechnology for example over absorbent distributor rollers 32 and 31 toan application roller 3 and thence to the surface of stone 5.

Appropriate application rollers, brushes, or even spray nozzles can beprovided for the sides of the stone. The advantage of applicationrollers over spraying the dispersion from all sides is that freshdispersion can constantly be applied, with the surface always acceptingthe amount appropriate to the particular previous drying process.

Since the impregnated surfaces are again force-dried in a another dryingsystem 4 downstream, the dispersant will set in outermost area 52,tightly sealing off the pores and capillary channels and not descendingundefined and irregularly into the deeper area 54.

In one practical further development of the method and device, the stoneis subjected to a coarse vacuum or preferably to low pressure prior toand especially during application of the dispersion.

Coating device 3, 31, 32, and 33 is accordingly enclosed in a vacuumchamber 7 that a suction pump 71 always maintains a partial vacuum in.There are locks 72 and 73 at the entrance and exit between conveyor 6and vacuum chamber 7. The locks can be elastic lip seals for examplethat match the cross-section of the stones and let them through as theyadvance.

FIG. 2 illustrates a stone saturated at its lower area 54 withdispersant M and at its upper area 52 with dispersion D. At the right ofthe picture is a graph cd, cm of concentration representing thesituation that occurs subject to the more powerful vacuum when the airemerges from area 52 and capillary force, gravity and, as the airreturns to the atmosphere, air pressure allow dispersion D to advance upto dispersant M.

The method can, as will be evident, also be employed for paving stonesthat are already in place, in which case, instead of the stones beingconveyed through the wetting, drying, and vacuum impregnation devices,the devices or processing media--dispersant, drying air, vacuum, anddispersion--are conveyed over the stones.

The devices can in this case be separate or, preferably, combined intoone component.

Furthermore, several impregnation processes or devices for the varioussurfaces can be carried out or positioned parallel or in series, withdifferent dispersants being employed in each case.

FIG. 3 illustrates an impregnation device with a conveyor 6' thatconsists of powered rollers 61 sloping down toward the middle on eachside of the path of conveyance. This device is employed for impregnatingthe bottom surface of the stones, and drying device 2 and 4 andapplication device 3 are accordingly located underneath. This systemmakes it possible to eliminated distributor rollers 31 and 32. Thepaving stones 5 are supported at their lower edges and advanced in thedirection of travel by rollers 61.

I claim:
 1. In a method of impregnating a plate (5) of a natural pavingstone, with a dispersed cross-linked plastic material, in which adispersion (D) of the material is applied to the surface (51) of theplate to be impregnated and the dispersant is substantially evaporated,the improvement wherein the plate (5) is extensively saturated with thepure dispersant (M) and subsequently only the surfaces (51: lateralsurfaces) of the plate that are to be saturated are force dried at anair temperature and speed and for a duration sufficient for an area (52)of a predetermined depth corresponding to a small fraction of thethickness of the plate to dry, and the dispersion (D) is then applied orsprayed in a regulated flow, over the surfaces (51) to be impregnated,followed by forced drying of the impregnated surfaces (51).
 2. Themethod as in claim 1, wherein the dispersion (D) is applied in a coarsevacuum or under low pressure.
 3. The method as in claim 1 or 2, whereinthe plate (5) is saturated with pure dispersant (M) while being cut andground or trimmed and cleaned of dust between being dried and having thedispersion (D) applied to it.
 4. The method as in claim, 1 or 2 whereinthe dispersant (M) is water and the dispersion (D) contains at least oneparticle and droplets on a basis of acrylic resin with a mean diameterthat is less than the mean pore width of the capillaries in the plate(d).
 5. A device for impregnating a plate of absorbent material with adispersed material, comprising: a conveyor (6) for moving plates (5) ina given direction, an application device for saturating the plates witha pure dispersant (M), an initial drying device (2) downstream of theapplication device and which consists of a blower with an air-flowregulator and a heat register (11) positioned in the stream of air andhaving an air-temperature regulator and which contains dry-air linesaimed at the surfaces (51) to be impregnated, a disperson-applicationdevice (3, 31, 32, and 33) downstream of the initial drying device thatcontains applicators that are associated with the surfaces to beimpregnated (51) and that accept the disperson (D) through means (32 and31) regulating flow, and release it to the surfaces (51) of the plates,and another drying device (4) downstream of the dispersion applicationdevice and that consists of a blower and dry-air lines aimed at thesurfaces (51) saturated with dispersion (D), wherein the drying outputof the another drying device (4) is at least equal to that of theinitial drying device (2).
 6. The device as in claim 5, wherein thedispersion-application device is enclosed in a vacuum chamber (7)connected to a coarse-vacuum or low-pressure suction device (71) andcomprising locks (72 and 73), including elastic lip seals, at anentrance and exit for the conveyor (6) to and from the chamber.
 7. Thedevice as in claim 5 or 6, wherein different dispersion-applicationdevices are associated with the different surfaces.
 8. The device as inclaim 5 or 6, wherein the application device comprises applicationrollers and the dispersion (D) is conveyed from a reservoir through alevel regulator into a tub (33) and wherein the regulating meanscomprises a distributor roller (32) that is mounted such that it canrotate with its surface immersed and in contact with the surface of atransfer roller (31) that is mounted such that it can rotate and thesurface of the transfer roller is in turn in contact with the surface ofthe application roller (3), and in that at least one of the rollers issynchronized with the conveyor (6).
 9. The device as in claim 5, furthercomprising a dust-removal brush and a suction device positioned at ordownstream of the initial drying device (2).
 10. The device as in claim5, wherein the conveyor (6) is a continuous horizontal conveyor beltthat the plates (5) lie on with their total surface, and has a drivemechanism with a speed that can be continuously or discontinuouslyvaried.
 11. The device as in claim 5, wherein the conveyor (6') consistsof powered rollers (61) sloping down toward the middle on each side of apath of conveyance and the drying and application devices (2, 3, and 4)are located underneath the conveyor (6').